HumpLog

SparkFun Humplog-Compatible Serial Data Logger

Overview

HumpLog is a serial data logger launched by HumpbackLab, compatible with the SparkFun OpenLog command set and usage model. Based on the AT32F421 Cortex-M4 microcontroller, it receives serial data via USART and records it in real-time to a MicroSD card (FAT filesystem), while supporting higher baud rates up to 1,000,000 baud and greater data throughput.

Core Features

• Fully Compatible - Compatible with the complete SparkFun OpenLog command set for seamless drop-in replacement
• High-Speed Recording - Supports up to 1 Mbps baud rate with verified reliable recording at ~74 KB/s
• Three Boot Modes - Supports newlog (auto-create new log files), seqlog (append to fixed file), and command (interactive shell)
• Flexible Configuration - All settings saved in config.txt on the SD card root, with real-time modification via the set command

Hardware Specifications

Component	Specification	Description
MCU	AT32F421G8U7	Cortex-M4, 64KB Flash, 16KB RAM
Storage Interface	SPI1 + MicroSD	FatFs filesystem, SPI mode
Serial	USART1	300–1,000,000 baud
Status Indicator	PB0 LED	Active-low, multiple blink patterns
Debug Interface	SWD	PA13 (SWDIO) / PA14 (SWCLK)

Supported Commands

Full compatibility with the following Humplog commands:

new · append · write · rm · size · read · cat · ls · md · cd · sync · init · reset · disk · baud · set · verbose · echo

LED Status Indicators

Mode	Data State	LED Behavior
newlog / append	Idle (>100ms no data)	Solid ON
newlog / append	Data writing	Fast blink (~20 Hz)
command / write	—	OFF
baud / set menu	—	OFF

Use Cases

• Flight Controller Logging - Record flight data for post-flight analysis and debugging
• Embedded System Debugging - Output debug logs to SD card via serial port
• Long-Term Data Acquisition - Ideal for continuous serial data recording scenarios
• Legacy Device Replacement - Drop-in replacement for the discontinued SparkFun OpenLog

Open Source & Resources

HumpLog is a fully open source project under the GPL-3.0 license. You can find the complete source code, hardware design files, and documentation on GitHub.

• GitHub Repository
• Hardware Schematic (PDF)

Issues, pull requests, and community contributions are welcome!

Purchase

Click the link below to purchase HumpLog Serial Data Logger:

Buy HumpLog on Taobao

Technical Support

For more technical support or product inquiries, please contact us through:

• GitHub: HumpbackLab
• QQ Group: 763833895
• YouTube: HumpbackLab